Preheat the oven to 350 degrees F (175 degrees C). Spray a glass baking dish (such as Pyrex®) with cooking spray.
Heat oil in a pan over medium-high heat. Add carrots, onions, and celery and saute until onions are translucent, 5 to 7 minutes.
At the same time, heat a large skillet over medium-high heat. Cook and stir ground beef in the hot skillet until browned and crumbly, 5 to 7 minutes. Drain and discard grease.
Move beef to one side of the skillet and melt butter over medium heat. Whisk in flour a little at a time until combined; whisk in milk, whisking constantly to prevent lumps. Stir in beef broth. Add sauteed vegetables, garlic salt, onion powder, garlic powder, and black pepper. Bring to a boil; cover and remove from heat.
Add buttermilk to baking mix. Stir until a soft dough forms. Place on waxed paper. Roll to 1/2-inch thickness. Cut with a 2 1/2-inch round biscuit cutter dipped in baking mix.
Pour the beef mixture into the prepared baking dish and top with biscuits.
Bake in the preheated oven until biscuits are browned, 24 to 25 minutes.